During a six year period, 1,953 fine needle aspiration cytologies (FNAC) were performed for lumps of the breast. Of these, 355 were diagnosed as carcinoma of the breast. The FNAC was performed on an outpatient basis and the pathologic interpretation was available within 30 to 60 minutes. The treatment strategy was always guided by the clinical impression of the physician. If the results of a suspected mass were negative on FNAC, biopsy was performed and histologic study gave the final diagnosis. There were no false-positive results and only 6 per cent were false-negative findings diagnosed later by open biopsy. The over-all accuracy rate was 90 per cent plus 4 per cent diagnosed on cytologic examination as "suspicious" and which proved to be malignant. Based upon our accumulated results, simplicity of performing the test, its low cost, the extremely low morbidity, the immediate response and, above all, an over-all high accuracy rate, we conclude that FNAC is a highly recommended method for the diagnosis of carcinoma of the breast.